My question is about the type restrictions on the polymorph spell. For example 1st level is restricted to animal and humanoid. But neither of these are listed under type and subtype in Appendix 3. So does this mean if I base my form off a specific creature that it needs to be an animal or humanoid? Can I base the form off an aberration and it just doesn't grant the creature type? Why grant creature types that don't grant bonuses as listed in the Appendix?
The "type and subtype" listing on pg. 144 only mentions those subtypes that give mechanical advantages related to the subtype. For other subtypes they only impose limitations (at 1st level if you pick a specific form to imitate for purposes of a bonus ability or disguise it must be humanoid or animal) and determine whether you can keep your weapons and armor when you transform (an aberration or monstrous humanoid PC who uses Polymorph 1 is always going to have his gear absorbed because he can't remain an aberration or monstrous humanoid).
Note that the subtypes that do grant bonuses aren't very good as by the time you're that level you probably have enhancement bonuses to saves that overlap with and don't stack with these bonuses. The exceptions are elemental (free fire immunity and immunity to flanking as options) and vermin (+4 enhancement to mind affect might very well be an improvement on your Ring of Resistance or Black Heart bonus).